The present invention relates to a stable aqueous dispersion of polymer particles containing sulfur acid functionality (a sulfur acid functionalized latex polymer). This dispersion is useful in coatings formulations.
Titanium dioxide (TiO2) is an expensive component of many coatings or paints. The efficacy of TiO2 as a hiding pigment is reduced when TiO2 particles are allowed to come too close together upon film formation and drying (which they tend to do). It has been disclosed that the spacing of TiO2 and its resultant efficiency can be improved using an adsorbing emulsion polymer.
U.S. Pat. No. 7,179,531 discloses polymer particles having select functional or absorbing groups useful for preparing organic-inorganic composite particles that are suitable for providing dried coatings with improved hiding. These organic-inorganic composite particles must remain stable in the coating or paint for long periods of time and withstand shear that is normally applied to coatings. This additional shear on finished coatings is often applied during the color tinting process or as mixing before paint is used. Although the polymer particles with absorbing groups may be stable when stored alone, the composite may be less stable. This instability can be further exacerbated by storing the paint at high temperatures in order to mimic long term shelf stability. Accordingly, it would be desirable to find improve the shelf stability of coating formulations that contain organic-inorganic composite particles.